1. Field of the Invention
This invention relates to an electro-luminescence device, and more particularly, to a mask for an organic electro-luminescence device and a method of fabricating the same that is capable of forming an organic layer having a special color without a damage of an organic layer formed on a substrate.
2. Description of the Related Art
Recently, there have been developed various flat panel display devices reduced in weight and bulk that is capable of eliminating disadvantages of a cathode ray tube (CRT). Such flat panel display devices include a liquid crystal display (LCD), a field emission display (FED), a plasma display panel (PDP) and an electro-luminescence (EL) display, etc. device.
In such flat panel display devices, the PDP has the most advantage for making a large dimension screen because its structure and manufacturing process are simple, but has a drawback in that it has low light-emission efficiency and large power consumption. The LCD has a difficulty in making a large dimension screen because it is fabricated by a semiconductor process, but has an expanded demand as it is mainly used for a display device of a notebook personal computer. However, the LCD has a drawback in that it has a difficulty in making a large dimension screen and it has large power consumption due to a backlight unit. Also, the LCD has characteristics of a large light loss and a narrow viewing angle due to optical devices such as a polarizing filter, a prism sheet, a diffuser and the like.
On the other hand, the EL display device is largely classified into an inorganic EL device and an organic EL device. When compared with the above-mentioned display devices, the EL display device has advantages of a fast response speed, large light-emission efficiency, a large brightness and a large viewing angle. The organic EL display device can display a picture at approximately 10[V] and a high brightness of ten thousands of [cd/m2].
FIG. 1 is a plan view illustrating a related art organic electro-luminescence (EL) display device, and FIG. 2 is a sectional view illustrating the organic EL display device taken along a line II-II′ in FIG. 1.
Referring to FIGS. 1 and 2, the related art organic EL display device comprises a insulating film 6, a barrier rib 8, and an organic layer 10, formed between an anode electrode 4 and a cathode electrode 12. The anode electrode 4 and the cathode electrode 12 are crossing so as to insulate from each other.
A plurality of anode electrodes 4 is provided on the substrate 2 in such a manner to be spaced at a predetermined distance from each other. A first driving signal is supplied to such the anode electrode 4 in order to emit an electron (or hole).
The insulating film 6 is formed in a lattice type so as to expose an aperture for each EL cell area on the substrate 2 having the anode electrode 4.
The barrier rib 8 is formed in a direction crossing the anode electrode 4, and is formed in parallel to the cathode electrode 12 by a predetermined distance to partition adjacent EL cells. In other words, the barrier rib 8 separates the organic layers 10 from each other and the cathode electrodes 12 from each other between the adjacent EL cells. Further, the barrier rib 8 has an overhang structure in which the upper portion thereof has a larger width than the lower portion thereof.
The organic layer 10 made from an organic compound on the insulating film 6. In other words, the organic layer 10 is formed by depositing a hole carrier layer, a light-emitting layer and an electron carrier layer onto the insulating film 6.
A plurality of cathode electrodes 12 is provided on the organic layer 10 in such a manner to be spaced at a predetermined distance from each other, and in such a manner to be crossed with the anode electrodes 4. A second driving signal is supplied to the cathode electrode 12 in order to emit an electron (hole).
The substrate 2 having the cathode electrode 12 is protected by use of a packaging plate 14. In other words, the packaging plate 14 covers the anode electrode 4, the cathode electrode 12, and the organic layer 10 formed on the substrate 2, by using an sealant (not shown), so as to prevent the organic layer 10 from being deteriorated by moisture and oxygen in the atmosphere. After pressuring the packaging plate 14 to the substrate 12 to encapsulate the anode electrode 4, the cathode electrode 12, and the organic layer 10, the sealant is hardened by irradiating an ultraviolet ray. After encapsulating, an inert gas is injected in a space formed by sealing the substrate 2 and the packaging plate 14. At this time, the encapsulated atmosphere is performed in a globe box or a vacuum chamber.
In the organic EL device, when the first and the second driving signals are respectively applied to the anode electrode 4 and the cathode electrode 12, an electron and a hole are emitted. The electron and the hole emitted from the anode electrode 4 and the cathode electrode 12 recombine in the organic layer 10, and at the same time, visible rays are generated. At this time, the generated visible rays are emitted to the exterior via the anode electrode 4, to thereby display a predetermined picture or image.
FIGS. 3A to 3C are sectional views illustrating a method of manufacturing a shadow mask used for forming the organic layer shown in FIG. 2.
Firstly, as shown in FIG. 3A, an upper photo-resist 54a and a lower photo-resist 54b are entirely printed on a front surface and a rear surface of the metal plate 52, respectively. A photo mask 50 having a shielding part 50b and a transmissive part 50a is arranged on each of the front surface and the rear surface of the metal plate 52 having the printed upper and lower photo-resists 54a and 54b. The upper and the lower photo-resists 54a and 54b are patterned through a photolithography process including an exposing process using a mask and a developing process, to thereby form an upper and a lower photo-resist patterns 56a and 56b, as shown in FIG. 3B. The metal plate 52 is etched by using the upper and the lower photo-resist patterns 56a and 56b, to thereby form a shadow mask 60 having an open part 60a and a blocking part 60b, as shown in FIGS. 3C and 4.
Red, green, and blue organ layers 10R, 10G, and 10B are formed by using the shadow mask 60. For instance, the blue organic layer 10B is described referring to FIGS. 5A and 5B.
Firstly, a shadow mask 60 having an open part 60a and a blocking part 60b is arranged on a substrate 1 having red and green organic layers 10R and 10G. The open part 60a of the shadow mask 60 is located at an area corresponding to an area where the blue organic 10B is being formed, and the blocking part 60b is located at an area hiding an area where the red and the green organic layers 10R and 10G are formed. A blue organic material is screen-printed by using the shadow mask 60. Thereby, the blue organic material passing the open part 60a of the shadow mask is separated from the red and the green organic layers 10R and 10G with a barrier rib (not shown) therebetween to form the blue organic layer 10B.
Meanwhile, the related art red, green, and blue organic layers 10R, 10G, and 10B are formed by using the shadow mask 60 on a substrate 1. In this case, as a distance between the shadow mask 60 and the substrate 1 becomes far, color purity between the adjacent EL cells becomes deteriorated. For instance, at the time that blue organic layer 10B is formed on the substrate 1 having the red and the green organic layers 10R and 10G, as the distance between the shadow mask 60 and the substrate 1 becomes far, a probability that the blue organic material is spread to adjacent red and green organic layers 10R and 10G becomes high. Accordingly, there is a problem that color purity is deteriorated.
In order to prevent the above problem, as shown in FIG. 5A, a first distance d1 between the shadow mask 60 and the substrate 2 relatively becomes short, to thereby form a first organic layer (e.x., the blue organic layer). In this case, because a second distance d2 formed between the shadow mask 60 and each of second organic layers (e.x., the red and the green organic layers) is closer than the first distance, a probability that the shadow mask 60 and the second organic layer are being contacted becomes high. Accordingly, there is a problem that the shadow mask 60 is separated from the second organic layer or a scratch is generated in the organic layer.